I cannot find much about Mabel in primary sources... There is the newspaper clipping of her leaving her husband Thomas in 1796
This prompted me to look at the 1790 census of Thetford, as it was from her household in Thetford that she absconded...
Once I saw the her Thomas Burnham family listed I looked elsewhere in the same Thetford list and saw that there was a David Saxton.
This David seems to be the same as found in ancestry dot com genealogies .
eg Moore Earp Nicholas Peck McCrae Milne Family 20130323 by
david moore
21 Jun 1781 Lebanon, Grafton, New Hampshire
David's father is Charles Sexton
David's mother is Rachel Waters
https://www.ancestry.com/family-tree/tree/54118766/family?cfpid=266...
No Mable is there...
For that matter... no FAG for Mable, No birth record for Mable, etc..